In Peter Jackson's 2002 adaptation of J.R.R. Tolkien's The Lord of the Rings: The Two Towers, the second installment in The Lord of the Rings trilogy, Gandalf the Grey returns as Gandalf the White. Gandalf had previously been seen by his companions in The Fellowship of the Ring falling to his doom with a demon of the ancient world, a Balrog, deep in the Mines of Moria. His return was a surprise to his cohorts as well as first-time readers and audiences. While the books might go into great detail as to how Gandalf was able to make his immaculate resurrection from the dead, Jackson did not spend more than a few minutes of screen time addressing this feat. This quick summary was effective for how much time the movies had to reasonably address such a huge event for Gandalf's character, but it still leaves a lot of questions.
Source：https://www.cbr.com/lord-of-the-rings-gandalf-white-origin/
